In mid-May, the Detroit 3 and the UAW -- which have a COVID-19 joint task force -- reinstated a requirement that employees wear masks in southeastern Michigan where there are high levels of COVID-19.
The task force said on Tuesday if a facility is in a high-risk county as identified by the Center for Disease Control (CDC) it "strongly recommends masking" but they will not be required.
GM said the change was effective immediately.
The Detroit 3 automakers had said in early March they would allow auto workers to stop wearing masks at workplaces where U.S. health officials said it was safe to do so.
CDC masking guidelines issued in February shifted from a focus on the rate of COVID-19 transmission to monitoring local hospitalizations, hospital capacity and infection rates.
The Detroit 3 did not mandate employees get vaccinated in the U.S. but recommended workers do so.